Materials
Available from the geoscience education department at Michigan Tech:
Large assortment of igneous, metamorphic, and sedimentary rocks
A limited number of fossils and casts
Porcelain streak plates
Other possible mineral assortments may be available through the Seaman Museum
Magnifying glasses

Procedure
What are the three types of rocks and how do they form?
The three types of rocks are igneous, sedimentary, and metamorphic.

Igneous rocks are volcanic in origin.  They form from the total melting and crystallization.  Explain Bowen's reaction series (for older students)--how different temperatures, compositions, and cooling rates form different igneous rock types.  Show some examples of igneous rocks.  Let the students feel and pick up each of the rocks.

Sedimentary rocks form from other rocks breaking apart.  Mention weathering and erosion.  Show some examples of sedimentary rocks and some sedimentary structures.  Ripple marks and mud cracks are good examples that the students can often related to.

Metamorphic rocks form from igneous and sedimentary rocks being put under high heat and pressure.  Show some examples.

How do geologists identify rocks and minerals?
Explain how each of the following can help identify a rock or mineral.
    Color:  explain that color can help but may be deceiving.
    Crystal size:  the larger the crystal, the slower the cooling.
    Hardness:  explain that this trait can be one of the best indicators.  Explain Moh's hardness scale.  Have the students identify a few rocks using the scale.
    Cleavage:  get some easy examples such as quartz (with no cleavage), mica (with one-sided cleavage), and calcite and fluorite (with multiple cleavages).
    Streak:  explain how streak can identify rocks.  Let the students use porcelain streak plates to identify a couple of rocks.  Hematite (iron) is a good one to use since it common to this area.

Show the students how a mild HCl solution can identify calcite and limestone and explain that this is a chemical reaction.

For sedimentary rocks, explain how sedimentary structures form and how grain size can be important.  Bring in some beach sand and a piece of sandstone.  Let the students use magnifying glasses to try and categorize a few sedimentary rocks.

How and when did fossils form?
Explain how fossils and casts came into existence and show some examples.  If time permits, show the geologic time scale.  Try and put some of the important dates into perspective on a 24-hour clock.  Dinosaurs came here, fish here, people here (if you want to touch that one!), etc.
 

Shawn Len, 2000.
 
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